We request funds for a multi-photon/confocal laser scanning confocal microscope in a shared imaging facility for the study of brain ans spinal cord injury. The facility will be operated and directed by a core group of four investigators within the Center for the Study of Nervous System Injury at Washington University. We utilize optical and electrophysiological approaches, together with ion- or oxidation- sensitive fluorescent probes, to understand mechanisms of hypoxic- ischemic injury, epilepsy, Alzheimer's disease, and other nervous system conditions. Previously our research focused on primary cell culture models, but we have extended our NIH-funded projects to include more intact model systems, including acute brain slice preparations and organotypic slice cultures. These models preserve cellular relationships and brain metabolic interactions, and offer the possibility of examining human tissue obtained at biopsy. The recent availability of transgenic mice with cell-specific expression of green fluorescent protein offers particularly exciting opportunities for dynamic observation of neurons and glia within living tissue. However, limitations in conventional optical microscopy preclude high resolution imaging in thick specimens. Two photon microscopy minimizes photodamage and light scattering, and allows sustained high-resolution dynamic imaging deep in brain slices. To take maximal advantage of these methodological developments, we seek full-time access to a laser scanning microscope within a dedicated facility which allows modifications for tissue perfusion, temperature and atmospheric control, and electrophysiology. We propose to acquire a commercial laser scanning confocal microscope with multiphoton capability, mode- locked sub-picosecond ti:sapphire laser, and upright physiology microscope. The system will be installed in an existing shared microscopy facility within the Center for the Study of Nervous System Injury. It will be supported by the Department of Neurology, and be accessible to core users and to scientists in the university community. Availability of multiphoton and confocal microscopy will promote new advances in understanding cell-cell interactions which lead to nervous system injury.